Alleen als bovenstaande is gedaan, kun je multisite studies gaan uitvoeren. One advantage of a multisite over a single site study is that the effects of treatment are examined in different sites that may have unique characteristics in terms of patient population, therapist characteristics, and so on. Generalizability of the results of treatment tot the clinical world is greater than in the single site study.


Another advantage: When disorder is rare, it may take years to get enough patients.